Method for apparatus for deriving maximum sub-block transform size

Abstract

The present disclosure provides apparatus and methods for signaling sub-block transform (SBT) information. The SBT information is used for coding video data. According to certain disclosed embodiments, an exemplary method includes: signaling a first flag in a Sequence Parameter Set (SPS) of a video sequence indicating whether a sub-block transform (SBT) is enabled; and signaling a second flag indicating a maximum transform block (TB) size that allows the SBT. A maximum coding unit (CU) size that allows the SBT is determined directly based on the maximum TB size in response to the first flag indicating that the SBT is enabled.

1 .- 20 . (canceled) 
     
     
         21 . A method of decoding a bitstream to output one or more pictures for a video sequence, the method comprising:
 decoding the bitstream;   determining, based on the decoded bitstream, a maximum transform size in luma samples; and   determining whether subblock transform (SBT) is allowed for a CU of the video sequence,   wherein the determining of whether the SBT is allowed for the CU is based on a comparison of a size of the CU to the maximum transform size in luma samples.   
     
     
         22 . The method according to  claim 21 , wherein:
 decoding the bitstream comprises decoding a flag associated with the video sequence; and   determining the maximum transform size in luma samples comprises determining the maximum transform size in luma samples based on a value of the flag.   
     
     
         23 . The method according to  claim 22 , wherein the flag is signaled in a sequence parameter set (SPS) of the bitstream. 
     
     
         24 . The method according to  claim 22 , wherein the flag is sps_max_luma_transform_size_64_flag. 
     
     
         25 . The method according to  claim 22 , further comprising:
 in response to a value of the flag being 1, determining the maximum transform size in luma samples to be equal to 64; or   in response to the value of the flag being 0, determining the maximum transform size in luma samples to be equal to 32.   
     
     
         26 . The method according to  claim 22 , further comprising:
 in response to the flag having a first value, determining the maximum transform size in luma samples to be equal to a second value; or   in response to the flag having a third value, determining the maximum transform size in luma samples to be equal to a fourth value.   
     
     
         27 . The method according to  claim 21 , wherein the comparison of the size of the CU to the maximum transform size in luma samples comprises at least one of:
 a comparison of a width of the CU to the maximum transform size in luma samples, or   a comparison of a height of the CU to the maximum transform size in luma samples.   
     
     
         28 . The method according to  claim 21 , further comprising:
 determining a maximum CU size that allows the SBT to be equal to the maximum transform size in luma samples.   
     
     
         29 . A method of encoding a video sequence into a bitstream, the method comprising:
 determining, for the video sequence, a maximum transform size in luma samples;   determining whether to use subblock transform (SBT) for a coding unit of the video sequence,   wherein the determining of whether to use the SBT for the CU is based on a comparison of a size of the CU to the maximum transform size in luma samples.   
     
     
         30 . The method according to  claim 29 , further comprising:
 encoding a flag indicating the maximum transform size in luma samples.   
     
     
         31 . The method according to  claim 30 , encoding the flag in a sequence parameter set (SPS) of a bitstream associated with the video sequence. 
     
     
         32 . The method according to  claim 30 , wherein the flag is sps_max_luma_transform_size_64_flag. 
     
     
         33 . The method according to  claim 30 , further comprising:
 in response to the maximum transform size in luma samples being determined to be equal to 64, setting a value of the flag to be 1; or   in response to the maximum transform size in luma samples being determined to be equal to 32, setting the value of the flag to be 0.   
     
     
         34 . The method according to  claim 30 , further comprising:
 in response to the maximum transform size in luma samples being determined to be equal to a first value, setting the flag to have a second value; or   in response to the maximum transform size in luma samples being determined to be equal to a third value, setting the flag to have a fourth value.   
     
     
         35 . The method according to  claim 29 , wherein the comparison of the size of the CU to the maximum transform size in luma samples comprises at least one of:
 a comparison of a width of the CU to the maximum transform size in luma samples, or   a comparison of a height of the CU to the maximum transform size in luma samples.   
     
     
         36 . A non-transitory computer readable storage medium storing a bitstream associated with a video sequence, wherein the bitstream is decodable by:
 determining, for the video sequence, a maximum transform size in luma samples; and   determining whether subblock transform (SBT) is allowed for a CU of the video sequence,   wherein the determining of whether the SBT is allowed for the CU is based on a comparison of a size of the CU to the maximum transform size in luma samples.   
     
     
         37 . The non-transitory computer readable storage medium according to  claim 36 , wherein the bitstream comprises:
 a flag indicating the maximum transform size in luma samples.   
     
     
         38 . The non-transitory computer readable storage medium according to  claim 37 , wherein the bitstream comprises:
 a sequence parameter set (SPS) associated with the video sequence, the flag being signaled in the SPS.   
     
     
         39 . The non-transitory computer readable storage medium according to  claim 37 , wherein the bitstream is decodable by:
 in response to a value of the flag being 1, determining the maximum transform size in luma samples to be equal to 64; or   in response to the value of the flag being 0, determining the maximum transform size in luma samples to be equal to 32.   
     
     
         40 . The non-transitory computer readable storage medium according to  claim 37 , wherein the bitstream is decodable by:
 in response to the flag having a first value, determining the maximum transform size in luma samples to be equal to a second value; or   in response to the flag having a third value, determining the maximum transform size in luma samples to be equal to a fourth value.